genirq: Add irq_get_trigger_type() to get IRQ flags

Drivers that want to get the trigger edge/level type flags for a given
interrupt have to call irq_get_irq_data(irq) to get the struct
irq_data and then irqd_get_trigger_type(irq_data) to obtain the IRQ
flags.

This is not only error prone but also unnecessary exposes the struct
irq_data to callers.

It's better to have an irq_get_trigger_type() function to obtain the
edge/level flags for an IRQ.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Acked-by: Grant Likely <grant.likely@linaro.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mips@linux-mips.org
Link: http://lkml.kernel.org/r/1371228049-27080-2-git-send-email-javier.martinez@collabora.co.uk


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>